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A hybrid algorithm for phasor estimation is proposed that is immune to dc offset and current transformer (CT) saturation problems. The algorithm utilizes partial sum (PS)-based and multistage least-squares (MLS)-based methods before and after CT saturation is detected, respectively. The MLS-based method is initiated when the third difference of the secondary current detects the start point of the first saturation period. The determination of each saturation period is based on the sum of the secondary current from the start point of the first saturation period. A least-squares (LS) technique estimates the dc offset parameters from the single-cycle difference of the secondary current in the unsaturated periods. Removal of dc offset from the secondary current yields the sinusoidal waveform portion. Finally, the LS technique is used once again to estimate the phasor from the sinusoidal waveform portion. The performance of the algorithm was evaluated for a-g faults on a 345-kV 100-km overhead transmission line. The Electromagnetic Transient Program was used to generate fault current signals for different fault angles and remanent fluxes. The performance evaluation shows that the proposed algorithm accurately estimates the phasor of a current signal regardless of dc offset and CT saturation. The paper concludes by describing the hardware implementation of the algorithm on a prototype unit based on a digital signal processor.

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This paper proposes the planning method for capacitor installation in a distribution system to reduce the installation costs and minimize the loss of electrical energy. The expected lifetime of devices with moving parts depends on the total number of operations, which affects the replacement period and replacement decisions for aging equipment under a limited budget. In this paper, the expected device lifetimes are included in the formulation, and the optimal operation status of the devices is determined using a genetic algorithm. The optimal numbers and locations for capacitor installation are determined based on the optimal operation status. Simulation results in a 69-bus distribution system show that the proposed technique performs better than conventional methods.

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